Drawing die



Patented Mar. 17, 1942 DRAWING DIE Frank J. Felton, Pittsburgh, Pa., assignor to Pressed Steel Car Company, Inc., Pittsburgh, Pa., a corporation of Pennsylvania No Drawing. Application February 13, 1941, Serial No. 378,773

3 Claims.

In the manufacture of drawn steel articles, particularly those made by a plurality of passes through drawing dies with or without the use of mandrels, the said dies deteriorate rapidly throu h wear. These dies heretofore have been made of steel which for maximum efliciency must be heat treated. Many of the afore-mentioned drawn steel articles are hot drawn, that is, the steel from which they are made is heated prior to being passed through the drawing dies. This heat in the steel being drawn, in combination with the reduction in cross sectional area of the shape being drawn, causes rapid deterioration and wear of the said drawing dies.

Because of the rapid deterioration of heat treated steels under the aforementioned conditions and the expense involved in manufacturing said heat treated steel dies, it has become cost. An object of the present invention is to 7 provide relatively inexpensive drawing die material.

Another object of the invention is to provide I a drawing die material which needs no heat treating and which has long life.

Cast iron would be the obvious answer when seeking for a cheap material. Cast iron containing graphitic carbon is too soft. Cast iron in which all of the carbon is in the combined form produces a hard cast iron and is usually known as white cast iron to distinguish it from grey iron which has most of its carbon in the graphitic form. Ordinary white cast iron, whilst being hard, is likewise very brittle. When, however, a drawing die made of this material is machined in a grinder and placed in a ,die holder it will give good results.

Commercial white cast iron is normally brittle,

is not readily machineable to a smooth surfaceand has a moderate hardness when used in a drawing die. Hardness is desirable for increasing the abrasive resistance of a'drawing die but it is most undesirable in that it immoderately increases the difllculties of machining. Heretofore, it has been known thatwhite cast iron to which has been added or more of manganese has greatly increased hardness but is exceeding- 1y brittle and can not be machined to a smooth surface by the ordinary metal cutting tool.

I have found that increasing the manganese content of white cast iron, which normally varies from to .70%, to less than 1.5% has little hardening efiect on the metal. I have also found that the higher the carbon content the less manincrease in the hardness of the metal. A manganesecontent of between 2% and 4% in White cast iron having a carbon content of 2% to 3% produces increased abrasive resistance over that of the commercial white cast iron whilst permitting and greatly increasing the machineability.

, Per cent Si .50 to .100 P 0.15 to 0.40 S, preferably less than 0.05 Mn 2 to 4 Combined carbon 2.50 to 3.00

will produce a cast iron which is exceptionally hard, has long wearing qualities, and can be readily machined either in a lathe or grinder. I have found that a cast iron to the aforegoing analysis has a BrinelPhardness of 400, which is approximately twice as much as is obtainedfrom the usual white cast iron. The total carbon content of the cast iron of my invention is higher than that of ordinary white cast iron and is all in the combined form. The manganesecontent of my cast iron has been very greatly increased 7 over that of the. ordinary white cast iron.

In the aforegoing analysis I have found the silicon and phosphorus may be varied within the limits given without any appreciable effect on the product, the sulphur being kept down below the limit as given. In cases where the cast iron is produced in a cupola instead of an open hearth furnace the sulphur content will of necessity be much greater for obvious reasons. I have found that the manganese when held to a minimum of 3% in combination with 2 /2% carbongives the best result and whilst it can be increased to 4 or even more percent, it produces an increased the carbon is decreased the manganese must be anese above 1.5% is necessary to produce an increased to retain the hardness and machineability. Thus 2% of carbon requires approximately 4% of manganese, whilst 3% of carbon requires approximately 2% of manganese.

Drawing dies made of cast iron of the foregoing analysis may be cast to substantially the desired shape and quickly machined to the finished sizes. They need no subsequent heat treating and, therefore, are'much more economical to manufacture. oi. the finished cost of my cast iron die to that of steel die is about 1 to 25, or as otherwise stated, may be produced at a cost of approximately $2.00 each as compared with a cost of $50.00 each for steel dies for drawing75 mm. shells. In a recent test of a number of draw dies made from the herein described cast iron in comparison with steel draw dies it was found the cast iron draw die would produce from twelve to eighteen hundred '75 mm. shell casings in comparison with less than half that number by a steel die of the type formerly used.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

I have found that the ratio 1. a drawing die blank of white cast iron having -a carbon content from 2% to 3%; a manganese content from 2% to 4% which increases within the range given as the carbon content within the range given is reduced; characterized by its ready machineability and abrasive resistant qualities.

2. A drawing die blank formed of cast metal I which is readily machineable and has marked abrasive resistant qualities comprising 2% to 3% total carbon in the combined form; manganese 2% to 4%; silicon .5% to 1.00%; phosphorus .15% to 30%; sulphur about .5% and the balance iron.

FRANK J. FELTON. 

